Russell, 40, and Rhys, 41, deflected questions about their relationship for months after hooking up on the set of their FX series in 2013, but finally appeared as a couple at NYC’s The Public Theater in April 2014.

“Matthew is really in love,” a source told Us. “They feel they should have always been together.”

Though Russell has never publicly gushed about Rhys, she has talked about what it’s like to act opposite the Welsh hunk. “What I enjoy is [Rhys] makes it so easy,” she told the Los Angeles Times in June 2014. “You feel you’re in safe hands, and it’s enjoyable to work like that because you’re sort of like, let him do all the hard stuff.”

Russell is already mom to son River, 8, and Willa, 4, with ex-husband Shane Deary, who she divorced in 2013 after almost seven years of marriage.